<html lang="zh-Hans">
<head>
  <meta charset="UTF-8" />
  <title>Document</title>
  <style>
    body {
      background: #000;
    }

    #container {
      width: 500px;
      height: 300px;
      display: flex;
      flex-wrap: wrap;
      background-color: rgb(255, 255, 255);
      align-items: flex-end;
      justify-content: space-around;
    }

    #my_id {
      width: 200px;
      height: 100px;
      background-color: rgb(255, 0, 0);
    }

    #container .c1 {
      /* flex: 1; */
      width: 100px;
      height: 50px;
      background-color: rgb(0, 255, 0);
      align-self: center;
    }
  </style>
</head>
<body>
  <div id="container">
    <div id="my_id"></div>
    <div class="c1"></div>
    <div class="c1"></div>
    <div class="c1"></div>
    <div class="c1"></div>
  </div>
</body>
</html>